Synchronize Router Clock with NTP

When it comes to time sensitive events like expiring of a digital certificate or the date range on an access-list, correct time is imperative or these features will act weird or not at all. So we use NTP/SNTP to synchronize the router clock with one of the many time servers out on the internet. First, we setup the correct timezone, for me that is Atlantic Standard Time (AST)

SC(config)#clock timezone AST -4

If your timezone takes part in daylight savings, we can enable that too. Note, older IOS versions use the old DST dates, if you  are running older code, you will have supply the dates for the start / end dates (or upgrade?). All code above that version uses the newer dates and the below command will work just fine. Check the Field Notice for more information.

SC(config)#clock summer-time ADT recurring

Allow NTP to change calendar date (Optional)

SC(config)#ntp update-calendar

Set the router to use our NTP server to sync its clock.

SC(config)#ntp server

Synchronization of the router clock is not only for digital certificates, but it will make the router logs a lot more useful if the timestamps are correct.

Sep 9th, 2010 • Posted in IOS, Management
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